1. Field of the Invention
The present invention relates to a rodless cylinder for transporting a workpiece or the like by displacing a slider in accordance with reciprocating motion of a piston.
2. Description of the Related Art
A rodless cylinder has been hitherto used, for example, as a means for conveying a workpiece. Such a rodless cylinder is disclosed, for example, in Japanese Laid-Open Patent Publication No. 9-273506 as follows. That is, a piston is inserted into a cylindrical cylinder tube so that the piston is slidable in an axial direction thereof. A plurality of driving magnets, which face the inner wall of the cylinder tube, are disposed on the outer circumference of the piston. On the other hand, a slider, which surrounds the cylinder tube, is provided movably outside the cylinder tube. Driven magnets, which are opposed to the driving magnets and which are slightly separated from the cylinder tube, are disposed on the inner circumference of the slider. A ball bush is provided inside the slider. A columnar guide shaft, which is provided in parallel to the cylinder tube, is inserted through the ball bush. The slider is held in a non-contact state with respect to the cylinder tube by the aid of the guide shaft.
When a pressure fluid such as compressed air is introduced into the cylinder tube, the piston is displaced in the axial direction at the inside of the cylinder tube. During this process, the driven magnets magnetically attract and repel the driving magnets. As a result, the slider is displaced along the outer circumference of the cylinder tube in accordance with the displacement of the piston in a state of being guided by the guide shaft.
The rodless cylinder constructed as described above makes it possible to decrease generation of dust or the like, because the cylinder tube and the slider make no contact with each other. Such a rodless cylinder is appropriately used, for example, for those relating to the medical field and the food as well as for the clean room used in semiconductor production steps.